Suez, Panama, Hormuz: How Chokepoint Closures Spike Freight Emissions
TL;DR
Three chokepoint events since 2021 produced measurable CO2 spikes. The Ever Given alone added around 300,000 tonnes of extra CO2 across diverted vessels. The 2023–2024 Houthi attacks pushed 60%+ of container traffic around the Cape for months. And the Panama drought cut daily transits from 36 to 24, forcing lighter loads and longer routes. If you report Scope 3 Category 4 emissions, these events hit your numbers directly.
I have spent eight years on the operations side of container shipping, and three of the most consequential disruption events of my career happened inside the past five. When the Ever Given ran aground in the Suez Canal for six days in March 2021, hundreds of vessels rerouted via the Cape of Good Hope, adding 3,000+ nautical miles per voyage. In late 2023, Houthi attacks on Red Sea shipping forced the same rerouting for months on end. Meanwhile, the Panama Canal drought of 2023-2024 cut daily transits by a third. Each disruption carried a direct, quantifiable CO2 cost — and if you report Scope 3 Category 4 freight emissions, those costs landed on your numbers whether you chose the diversion or not.
Suez Canal: 3,000 Extra Nautical Miles Per Voyage
The Suez Canal saves approximately 3,000 nautical miles on the Asia-to-Europe route compared to sailing around the Cape of Good Hope. Roughly 20,000 ships transit it each year, carrying 12-15% of global trade.
The Ever Given (March 2021)
A single grounded container ship blocked the canal for six days, holding up an estimated $9.6 billion in trade per day. Over 400 vessels queued at each end, and dozens diverted around Africa.
Estimated extra CO2: ~300,000 tonnes across affected vessels (derived from vessel tracking data and IMO Fourth GHG Study emission factors).
Houthi Attacks (Late 2023 - 2024)
Sustained attacks on commercial vessels in the Red Sea forced major carriers -- Maersk, MSC, Hapag-Lloyd, CMA CGM -- to reroute around the Cape for months. Container traffic through Suez dropped by over 60%.
Each rerouted large container vessel (8,000+ TEU) burns roughly 150-200 tonnes of fuel per day. Over the extra 10-14 days at sea, that is 1,500-2,800 additional tonnes of fuel -- translating to approximately 4,700-8,700 tonnes of CO2 per vessel per voyage.
Panama Canal: Drought, Lighter Loads, More Voyages
The Panama Canal connects the Atlantic and Pacific oceans, saving roughly 8,000 nautical miles compared to sailing around Cape Horn at the tip of South America. It depends on freshwater from Gatun Lake to operate its lock system.
In 2023-2024, an El Nino-driven drought pushed Gatun Lake to record-low levels. The Panama Canal Authority cut daily transits from 36 to 24 and imposed strict draft limits. Vessels had three options, all of them bad for emissions:
1. Wait in queue
Ships burned fuel at anchor for days. Some carriers paid $4 million+ at auction to skip the line -- a cost eventually passed to cargo owners.
2. Lighten the load
Draft restrictions meant vessels carried less cargo per transit. Lighter loads = more voyages needed to move the same volume = more emissions per tonne carried.
3. Reroute via Cape Horn or Suez
Cape Horn adds ~8,000 nm. Some US East Coast-to-Asia cargo went via Suez instead, adding distance and congestion to an already-strained waterway.
Strait of Hormuz: 21% of Global Oil Through a 33 km Gap
The Strait of Hormuz carries 21% of global petroleum liquids according to the U.S. Energy Information Administration. At just 33 km wide at its narrowest, it is the single most important energy chokepoint on Earth.
If Hormuz were closed, tankers would need to reroute via the Cape of Good Hope, adding approximately 6,400 km to voyages bound for Europe. For nearby destinations like India, the detour is proportionally even more extreme — a 1,200 nm trip to Mumbai becomes 14,500+ nm via the Cape. The 6,400 km figure is the average; specific lanes such as the Jebel Ali – Rotterdam route roughly double in distance when the strait is bypassed.
We cover the full CO2 math — emission factors per vessel class, distance deltas, and fuel burn estimates — in our deep-dive post on Hormuz.
Why This Matters for Scope 3 Reporting
These disruptions don't only affect shipping lines. If you are a cargo owner reporting Scope 3 Category 4 (upstream transportation and distribution) emissions, your reported numbers spike when your carriers reroute -- even if you had no say in the decision.
Under the GHG Protocol, Category 4 emissions should reflect the actual transportation activity, not just a planned route. When a vessel takes the Cape instead of Suez, your per-shipment carbon footprint can jump 40-60% overnight. The maths is anchored in GLEC Framework v3.2 container-vessel factors applied to the actual sailed distance — not the planned great-circle distance the booking system originally reflected.
The Reporting Gap
Most companies calculate freight emissions using planned routes and average distances. During disruptions, these estimates undercount actual emissions by thousands of tonnes. Without real-time route data feeding into your emission calculations, your Scope 3 reports will be wrong exactly when accuracy matters most.
You Can't Predict Geopolitics. You Can Measure the Impact.
No logistics team could have predicted the Ever Given grounding, the Houthi campaign, or the severity of the Panama drought. These events are, by nature, unpredictable.
But you can measure the emission impact of route changes in real time with the right tools. When your carrier notifies you of a rerouting, you should be able to recalculate your shipment's CO2 footprint within minutes — not wait until your annual sustainability report to discover the delta. Our team has wired the recalculation into our freight emissions API so the actual sailed distance flows straight into the Category 4 number rather than waiting for the next reporting cycle.
For a detailed walkthrough of how we turn route distances and cargo weights into emission numbers, see How We Calculate Emissions. The connection between chokepoint diversions and fuel-burn arithmetic also runs through the cubic speed-fuel curve — when carriers redirect via the Cape, the same diversion typically accompanies a slow-steaming decision to limit the operational-cost penalty, which complicates the per-voyage CO2 arithmetic in both directions.
One acknowledged gap
The CO2 deltas I have cited here assume diverted vessels run at their pre-disruption design speed. In practice, carriers facing a Cape diversion often pair the longer routing with a 1-2 knot speed reduction to offset the schedule-extension penalty. That lowers fuel burn per voyage day but extends voyage time, and the two effects partially cancel out. My per-voyage 4,700-8,700 tCO2 figure is therefore a working upper bound; carriers reporting primary-data emissions during disruption windows typically land 10-20% lower than the design-speed maths predicts.
Re-cost a diverted voyage
Toggle the same lane from Suez to Cape of Good Hope and the calculator returns the CO2 delta against GLEC v3.2 vessel factors. See the methodology for the math behind each emission factor and route distance.